AMYGDALA 



I4I3 



metamorphosis.' This is a strong urge to attend and to 

 react to every visual stimulus. Some observers also 

 noted this change after more restricted lesions in- 

 volving mainly the amygdala (29, 220, 223). Others 

 failed to see it (199, 249). 



Strong oral tendencies, an urge to examine all 

 objects by mouth, whether edible, inedible, dangerous 

 or even disgusting, is another prominent behavioral 

 change seen in Kliiver & Bucy's monkeys (143-145) 

 and is also reported by many investigators to occur 

 after more restricted lesions involving principally the 

 amygdala (17, 29, 202, 204, 216, 220, 222, 223, 234, 

 252). Others however did not obser\e this change 

 (199, 240). This "oral compulsive behavior' may be 

 closely related to two other components of the 

 Kliiver-Bucy syndrome: first, visual agnosia which 

 may represent a compensating mechanism aimed at 

 object discrimination by taste, smell and touch; and 

 second, disturbances in feeding behavior manifested 

 by a compulsive urge to ingest anything indiscrimi- 

 nately (216). One may object to this interpretation on 

 the ground that usually inedible objects are discarded 

 after oral examination. This is however not always 

 the case and may in any event not be very relevant 

 an objection since meat, which a normal monkey 

 would not 'consider' edible, is accepted as food by 

 bilaterally amygdalectomized monkeys (204, 252). 

 The actual amount of food intake is described as 

 normal by some authors (10, 18, 220, 254) and as 

 increased by others (204, 217, 240). 



Visual agnosia is the only symptom of the Kliiver- 

 Bucy syndrome which most probably is not critically 

 dependent on an amygdaloid lesion as shown by 

 Pribram and his associates (183, 204, 252). However, 

 Sawa and co-workers (220) mention its occurrence 

 after bilateral amygdaloid lesions in man. 



The changes produced by bilateral amygdaloid 

 lesions are not static. The)' evolve in time. Immedi- 

 ately after operation there is often a sleep-like or 

 cataleptic state with apathy and refusal to eat (lo, 16, 



17. 29. '99' 202, 223, 227, 234, 240, 249, 252) 



How- 



ever hyperactive and overaggressive behavior imme- 

 diately after operation was observed by some other 

 investigators (220, 236). After several days the post- 

 operative apathy clears up and the profound changes 

 in emotional behavior become apparent. Hyper- 

 sexuality develops only after several weeks or even 

 months (145, 223). Over months or years the be- 

 havioral alterations tend to recede slowly. In monkeys 

 hypersexuality and meat-eating are the first to disap- 

 pear (141), whereas the changes in emotional be- 

 havior and hypermetamorphosis are the most resistent 



(141, 240, 249) and may still Ije present after many 

 years (141). 



The changes produced by bilateral amygdalectomy 

 may be partly at least the consequence of some 

 release of the activity of the ventromedial hypo- 

 thalamic nucleus since its bilateral destruction in 

 amygdalectomized animals restores aggressiveness and 

 abolishes hypersexuality, oral compulsive behavior 

 and hypermetamorphosis (222, 223). This would 

 indicate that the pathways from the amygdala to 

 this nucleus, demonstrated with anatomical (3) and 

 electrographic (96) methods, mediate an inhibitory 

 influence. 



P.ATHOPHYSIOLOGY 



Epilepsy 



Revealing insights into the functions of the amyg- 

 dala can be gained from studies of epileptic seizures 

 originating in this area. It was Hughlings Jackson 

 (i 23-1 26) who first recognized late in the last century* 

 that seizure discharge originating from this area 

 produces what today is called psychomotor epilepsy 

 (74, 78, 94, 95) or temporal lobe epilepsy with ictal 

 automatism (61, 86, 197, 198). Recent work has 

 clearly demonstrated the correctness of Hughlings 

 Jackson'sviews(58, 61, 71, 74, 75, 78,83,92, 127-129, 

 134, 176, 179, 181, 198). 



The most characteristic feature of the automatic 

 state, so typical of these attacks, is the patient's "loss 

 of capacity to make durable memory records" [Pen- 

 field (198); (see also 159)]. This is usually associated 

 with unresponsiveness and a variable degree of loss of 

 understanding, which one may call confusion, while 

 motor control and reception of sensory stimuli is 

 preserved. Thus the patient may be able to indulge in 

 self-inspection or carry out elaborate acts and even 

 avoid obstacles when moving around. If he talks at 

 all, his speech is usually irrelevant to the situation. 

 When interfered with, he often becomes aggressive. 

 Masticatory movements, respiratory and autonomic 

 changes are commonly observed during such an 

 attack. The seizure usually starts with sudden staring, 

 less often with tonic adversive movements, and is 

 often ushered in by an epigastric, cephalic, somatic, 

 gustatory or olfactory sensation, a feeling of fear, and 

 awareness of confusion of thinking or a "psychical' 

 illusion (40, 61, 75, 84, 86, 174, 176, 197, 198). More 

 rarely observed ictal symptoms are outbursts of rage 



' Even older descriptions of seizures originating in this area 

 were given by Sander in 1874 (219), Hamilton in 1882 (110) 

 and .Anderson in 1887 (19). 



